Closed bias air film riding seal in event of housing breach for shared engine lubrication accessory gearboxes

Abstract

A system includes a case, a stator, a ring seal, and a rotor and is configured to pump air out of a housing. The case is mounted on the housing. The stator is mounted within the case and has two sides, an inner diameter and an outer diameter, where the first side faces the case. The ring seal is disposed between the stator first side and the case. The rotor is mounted on a shaft and has a side facing the stator first side. The rotor side has grooves, an inner and outer peripheral surfaces, and is configured to pump air from the outer peripheral surface to the inner peripheral surface to thereby pump air out of the housing. The stator inner diameter is configured and the ring seal is positioned such that separation forces are substantially equal to or less than closing forces during a system breach.

1 . A lubrication system for supplying lubricant between a first housing and a second housing, the first and second housings each comprising air and lubricant, the system comprising:
 a lubricant supply tube extending at least partially through the second housing and configured to receive a supply of lubricant from the first housing;   an output shaft rotationally mounted within the second housing;   a seal assembly mounted to the output shaft and disposed within the second housing, the seal assembly configured to pump at least a portion of the air out of the second housing and comprising:
 a seal case mounted on the second housing; 
 a seal stator mounted within the seal case, the seal stator having a first side, a second side, an inner diameter and an outer diameter, the first side facing the seal case; 
 a ring seal disposed between the seal stator first side and the seal case; and 
 a seal rotor mounted on the output shaft and having a side facing the seal stator first side, the seal rotor side having an inner peripheral surface and an outer peripheral surface, the seal rotor configured to pump air from the outer peripheral surface to the inner peripheral surface to thereby pump the air out of the second housing and includes grooves formed therein, 
 wherein during a breach of at least one of the first and the second housings: 
 a first force is exerted on the stator in a first direction by an air film generated by the seal rotor; 
 a second force is exerted on the stator in the first direction by a differential engine pressure from the seal stator inner diameter to the groove; 
 a third force is exerted on the seal stator in a second direction opposite the first direction by a differential engine pressure from the seal stator inner diameter to the ring seal; 
 a fourth force is exerted on the seal stator in the second direction by a differential engine pressure across the ring seal; 
 a fifth force is exerted on the seal stator in the second direction by the spring; and 
 the seal stator inner diameter is configured and the ring seal is positioned such that separation forces comprising the first and the second forces are substantially equal to or less than closing forces comprising the third, the fourth, and the fifth forces. 
   
     
     
         2 . The lubrication system of  claim 1 , wherein the ring seal is an o-ring. 
     
     
         3 . The lubrication system of  claim 1 , wherein the ring seal is a C-seal. 
     
     
         4 . The lubrication system of  claim 1 , wherein the ring seal comprises a diaphragm. 
     
     
         5 . The lubrication system of  claim 1 , wherein the ring seal comprises a metal bellows. 
     
     
         6 . The lubrication system of  claim 1 , wherein the seal rotor further comprises a seal layer coupled to the seal rotor side and the grooves are formed in the seal layer. 
     
     
         7 . The lubrication system of  claim 1 , wherein the seal rotor includes a coating thereon and the coating comprises a high hot hardness material. 
     
     
         8 . The lubrication system of  claim 7 , wherein the high hot hardness material is selected from the group consisting of carbide cobalt, chrome carbide nickel chrome, chrome oxide, or chrome plating. 
     
     
         9 . The lubrication system of  claim 1 , wherein the seal stator comprises carbon and a phosphate antioxidant.
 a filter coupled to the return opening to thereby remove at least a portion of the contaminants from the lubricant.   
     
     
         10 . The lubrication system of  claim 1 , the system further comprising:
 a check valve disposed within the second housing and configured to provide a seal between the first and second housings in response to a pressure differential therebetween.   
     
     
         11 . A lubrication system for supplying lubricant between a first housing and a second housing, the lubricant supplied by a lubricant supply tube extending at least partially through the second housing and configured to receive a supply of lubricant from the first housing, and an output shaft rotationally mounted within the second housing, the first and second housings each comprising air and lubricant, the system comprising:
 a seal case mounted on the second housing;   a seal stator mounted within the seal case, the seal stator having a first side, a second side, an inner diameter and an outer diameter, the first side facing the seal case;   a ring seal disposed between the seal stator first side and the seal case; and   a seal rotor mounted on the output shaft and having a side facing the seal stator first side, the seal rotor side having groove formed therein, an inner peripheral surface, and an outer peripheral surface, the seal rotor configured to pump air from the outer peripheral surface to the inner peripheral surface to thereby pump the air out of the second housing,
 wherein during a breach of at least one of the first and the second housings: 
 a first force is exerted on the stator in a first direction by an air film generated by the seal rotor; 
 a second force is exerted on the stator in the first direction by a differential engine pressure from the seal stator inner diameter to the groove; 
 a third force is exerted on the seal stator in a second direction opposite the first direction by a differential engine pressure from the seal stator inner diameter to the ring seal; 
 a fourth force is exerted on the seal stator in the second direction by a differential engine pressure across the ring seal; 
 a fifth force is exerted on the seal stator in the second direction by the spring; and 
 the seal stator inner diameter is configured and the ring seal is positioned such that separation forces comprising the first and the second forces are substantially equal to or less than closing forces comprising the third, the fourth, and the fifth forces. 
   
     
     
         12 . The lubrication system of  claim 11 , wherein the ring seal is an o-ring. 
     
     
         13 . The lubrication system of  claim 11 , wherein the ring seal is a C-seal. 
     
     
         14 . The lubrication system of  claim 11 , wherein the ring seal comprises a diaphragm. 
     
     
         15 . The lubrication system of  claim 11 , wherein the ring seal comprises a metal bellows. 
     
     
         16 . The lubrication system of  claim 11 , wherein the seal rotor further comprises a seal layer coupled to the seal rotor side and the grooves are formed in the seal layer. 
     
     
         17 . The lubrication system of  claim 11 , wherein the seal rotor includes a coating thereon and the coating comprises a high hot hardness material. 
     
     
         18 . The lubrication system of  claim 17 , wherein the high hot hardness material is selected from the group consisting of carbide cobalt, chrome carbide nickel chrome, chrome oxide, or chrome plating.